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<BODY><H2><a href="../contents.htm">Tcl8.6.11/Tk8.6.11 Documentation</a> <small>&gt;</small> <a href="contents.htm">Tcl Commands</a> <small>&gt;</small> pid</H2>
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<H3><A NAME="M2">NAME</A></H3>
pid &mdash; Retrieve process identifiers
<H3><A NAME="M3">SYNOPSIS</A></H3>
<B>pid </B>?<I>fileId</I>?<BR>
<H3><A NAME="M4">DESCRIPTION</A></H3>
If the <I>fileId</I> argument is given then it should normally
refer to a process pipeline created with the <B><A HREF="../TclCmd/open.htm">open</A></B> command.
In this case the <B>pid</B> command will return a list whose elements
are the process identifiers of all the processes in the pipeline,
in order.
The list will be empty if <I>fileId</I> refers to an open file
that is not a process pipeline.
If no <I>fileId</I> argument is given then <B>pid</B> returns the process
identifier of the current process.
All process identifiers are returned as decimal strings.
<H3><A NAME="M5">EXAMPLE</A></H3>
Print process information about the processes in a pipeline using the
SysV <B>ps</B> program before reading the output of that pipeline:
<P>
<PRE>set pipeline [open &quot;| zcat somefile.gz | grep foobar | sort -u&quot;]
# Print process information
exec ps -fp [<B>pid</B> $pipeline] &gt;@stdout
# Print a separator and then the output of the pipeline
puts [string repeat - 70]
puts [read $pipeline]
close $pipeline</PRE>
<H3><A NAME="M6">SEE ALSO</A></H3>
<B><A HREF="../TclCmd/exec.htm">exec</A></B>, <B><A HREF="../TclCmd/open.htm">open</A></B>
<H3><A NAME="M7">KEYWORDS</A></H3>
<A href="../Keywords/F.htm#file">file</A>, <A href="../Keywords/P.htm#pipeline">pipeline</A>, <A href="../Keywords/P.htm#process identifier">process identifier</A>
<div class="copy">Copyright &copy; 1993 The Regents of the University of California.
<BR>Copyright &copy; 1994-1996 Sun Microsystems, Inc.
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